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Subject[tip:perf/core] perf: Remove useless atomic_t
Commit-ID:  d9494cb4299da66541a3f3ab82c552889bee0606
Gitweb: http://git.kernel.org/tip/d9494cb4299da66541a3f3ab82c552889bee0606
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 17 Oct 2013 15:36:19 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 29 Oct 2013 12:02:49 +0100

perf: Remove useless atomic_t

There's nothing atomic about atomic_set vs atomic_read; so remove the
atomic_t usage.

Also, make running_sample_length static as it really is (and should
be) local to this translation unit.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: eranian@google.com
Cc: Don Zickus <dzickus@redhat.com>
Cc: jmario@redhat.com
Cc: acme@infradead.org
Cc: dave.hansen@linux.intel.com
Link: http://lkml.kernel.org/n/tip-vw9lg588x1ic248whybjon0c@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/events/core.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5bd7fe4..028dad9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -175,8 +175,8 @@ int sysctl_perf_event_sample_rate __read_mostly = DEFAULT_MAX_SAMPLE_RATE;
static int max_samples_per_tick __read_mostly = DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);
static int perf_sample_period_ns __read_mostly = DEFAULT_SAMPLE_PERIOD_NS;

-static atomic_t perf_sample_allowed_ns __read_mostly =
- ATOMIC_INIT( DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100);
+static int perf_sample_allowed_ns __read_mostly =
+ DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;

void update_perf_cpu_limits(void)
{
@@ -184,7 +184,7 @@ void update_perf_cpu_limits(void)

tmp *= sysctl_perf_cpu_time_max_percent;
do_div(tmp, 100);
- atomic_set(&perf_sample_allowed_ns, tmp);
+ ACCESS_ONCE(perf_sample_allowed_ns) = tmp;
}

static int perf_rotate_context(struct perf_cpu_context *cpuctx);
@@ -228,14 +228,15 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
* we detect that events are taking too long.
*/
#define NR_ACCUMULATED_SAMPLES 128
-DEFINE_PER_CPU(u64, running_sample_length);
+static DEFINE_PER_CPU(u64, running_sample_length);

void perf_sample_event_took(u64 sample_len_ns)
{
u64 avg_local_sample_len;
u64 local_samples_len;
+ u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);

- if (atomic_read(&perf_sample_allowed_ns) == 0)
+ if (allowed_ns == 0)
return;

/* decay the counter by 1 average sample */
@@ -251,7 +252,7 @@ void perf_sample_event_took(u64 sample_len_ns)
*/
avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;

- if (avg_local_sample_len <= atomic_read(&perf_sample_allowed_ns))
+ if (avg_local_sample_len <= allowed_ns)
return;

if (max_samples_per_tick <= 1)
@@ -262,10 +263,9 @@ void perf_sample_event_took(u64 sample_len_ns)
perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;

printk_ratelimited(KERN_WARNING
- "perf samples too long (%lld > %d), lowering "
+ "perf samples too long (%lld > %lld), lowering "
"kernel.perf_event_max_sample_rate to %d\n",
- avg_local_sample_len,
- atomic_read(&perf_sample_allowed_ns),
+ avg_local_sample_len, allowed_ns,
sysctl_perf_event_sample_rate);

update_perf_cpu_limits();

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